linux-kernel - [PATCH 3.16 239/305] xtensa: fix coprocessor part of ptrace

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Message-ID: <lsq.1549201508.301350733@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Max Filippov" <jcmvbkbc@...il.com>
Subject: [PATCH 3.16 239/305] xtensa: fix coprocessor part of
 ptrace_{get,set}xregs

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Max Filippov <jcmvbkbc@...il.com>

commit 38a35a78c5e270cbe53c4fef6b0d3c2da90dd849 upstream.

Layout of coprocessor registers in the elf_xtregs_t and
xtregs_coprocessor_t may be different due to alignment. Thus it is not
always possible to copy data between the xtregs_coprocessor_t structure
and the elf_xtregs_t and get correct values for all registers.
Use a table of offsets and sizes of individual coprocessor register
groups to do coprocessor context copying in the ptrace_getxregs and
ptrace_setxregs.
This fixes incorrect coprocessor register values reading from the user
process by the native gdb on an xtensa core with multiple coprocessors
and registers with high alignment requirements.

Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/xtensa/kernel/ptrace.c | 42 +++++++++++++++++++++++++++++++++----
 1 file changed, 38 insertions(+), 4 deletions(-)

--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -124,12 +124,37 @@ int ptrace_setregs(struct task_struct *c
 }
 
 
+#if XTENSA_HAVE_COPROCESSORS
+#define CP_OFFSETS(cp) \
+	{ \
+		.elf_xtregs_offset = offsetof(elf_xtregs_t, cp), \
+		.ti_offset = offsetof(struct thread_info, xtregs_cp.cp), \
+		.sz = sizeof(xtregs_ ## cp ## _t), \
+	}
+
+static const struct {
+	size_t elf_xtregs_offset;
+	size_t ti_offset;
+	size_t sz;
+} cp_offsets[] = {
+	CP_OFFSETS(cp0),
+	CP_OFFSETS(cp1),
+	CP_OFFSETS(cp2),
+	CP_OFFSETS(cp3),
+	CP_OFFSETS(cp4),
+	CP_OFFSETS(cp5),
+	CP_OFFSETS(cp6),
+	CP_OFFSETS(cp7),
+};
+#endif
+
 int ptrace_getxregs(struct task_struct *child, void __user *uregs)
 {
 	struct pt_regs *regs = task_pt_regs(child);
 	struct thread_info *ti = task_thread_info(child);
 	elf_xtregs_t __user *xtregs = uregs;
 	int ret = 0;
+	int i __maybe_unused;
 
 	if (!access_ok(VERIFY_WRITE, uregs, sizeof(elf_xtregs_t)))
 		return -EIO;
@@ -137,8 +162,13 @@ int ptrace_getxregs(struct task_struct *
 #if XTENSA_HAVE_COPROCESSORS
 	/* Flush all coprocessor registers to memory. */
 	coprocessor_flush_all(ti);
-	ret |= __copy_to_user(&xtregs->cp0, &ti->xtregs_cp,
-			      sizeof(xtregs_coprocessor_t));
+
+	for (i = 0; i < ARRAY_SIZE(cp_offsets); ++i)
+		ret |= __copy_to_user((char __user *)xtregs +
+				      cp_offsets[i].elf_xtregs_offset,
+				      (const char *)ti +
+				      cp_offsets[i].ti_offset,
+				      cp_offsets[i].sz);
 #endif
 	ret |= __copy_to_user(&xtregs->opt, &regs->xtregs_opt,
 			      sizeof(xtregs->opt));
@@ -154,6 +184,7 @@ int ptrace_setxregs(struct task_struct *
 	struct pt_regs *regs = task_pt_regs(child);
 	elf_xtregs_t *xtregs = uregs;
 	int ret = 0;
+	int i __maybe_unused;
 
 	if (!access_ok(VERIFY_READ, uregs, sizeof(elf_xtregs_t)))
 		return -EFAULT;
@@ -163,8 +194,11 @@ int ptrace_setxregs(struct task_struct *
 	coprocessor_flush_all(ti);
 	coprocessor_release_all(ti);
 
-	ret |= __copy_from_user(&ti->xtregs_cp, &xtregs->cp0,
-				sizeof(xtregs_coprocessor_t));
+	for (i = 0; i < ARRAY_SIZE(cp_offsets); ++i)
+		ret |= __copy_from_user((char *)ti + cp_offsets[i].ti_offset,
+					(const char __user *)xtregs +
+					cp_offsets[i].elf_xtregs_offset,
+					cp_offsets[i].sz);
 #endif
 	ret |= __copy_from_user(&regs->xtregs_opt, &xtregs->opt,
 				sizeof(xtregs->opt));